Bar code scanners are used in a wide variety of applications that rely on bar codes to store information. Industries such as retail, airline, self-service, automotive, parcel delivery, pharmaceutical, healthcare and others use optical codes to provide inventory control, customer identification, item tracking, security and many other functions. A bar code is read or scanned by a bar code scanner. The bar code is attached to or printed on an object and contains information about or related to the object. A typical bar code is comprised of a number of bars separated by spaces. Information is encoded on a bar code by varying the width of the bars and spaces. When a bar code is placed within the field of view of a bar code scanner, the scanner will detect, analyze and decode the bars and spaces comprising the bar code to retrieve the information encoded in the bar code. This operation is also called scanning or reading a bar code. The information encoded on a bar code is usually a sequence of numeric or alphanumeric numbers e.g., a Universal Product Code (UPC) or European Article Number (EAN).
An imaging bar code scanner (also referred to as an image scanner) reads a bar code by capturing a digital image of the bar code and then processing the image to detect and decode the bar code. It is advantageous for the bar code scanner to successfully read all bar codes presented to the scanner on the bar codes first pass by the scanner. This is known as a successful first pass read. Successful first pass reads of bar codes helps to maintain a good workflow at the checkout station and speeds up the overall checkout process. A high first pass read success rate has also been found to reduce stress on the person operating the scanner. This is particularly true if the operator is a customer operating a self-checkout terminal.
The percentage of successful first pass reads for an imaging scanner is negatively affected as the bar code passby speed increases. As the passby speed of a bar code increases, the image of the bar code captured by the image scanner starts to blur. The blurring reduces the ability of the image scanner to accurately detect and decode the bar code thus reducing the number of successful first pass reads. Because of external factors such as bar code size, bar code fidelity, illumination and bar code orientation to the scanner, the maximum passby speed for a successful first pass read will vary greatly. Since these and other factors are outside the control of the image scanner, it is important to reduce blurring as much as possible using methods that are controlled by the image scanner in order to achieve a high first pass read of a bar code.